diff --git a/AC-Vector.cabal b/AC-Vector.cabal
--- a/AC-Vector.cabal
+++ b/AC-Vector.cabal
@@ -1,6 +1,6 @@
 Cabal-Version: >= 1.6
 Name:          AC-Vector
-Version:       1.2.1
+Version:       1.2.2
 Stability:     Experimental
 Synopsis:      Efficient geometric vectors.
 
@@ -12,10 +12,9 @@
 
   Changes:
 
-  * Operator '*<>' has been renamed '|*' (and there's a
-    matching '*|' operator now too).
-
-  * There is now a 'vnormalise' function.
+  * /All prior versions/ of this library have a faulty
+    implementation of 'vcross'. Specifically, the sign of
+    the Y-coordinate is inverted. Oops!
 
 Category:      Data, Math, Numerical
 License:       BSD3
diff --git a/Data/Vector.hs b/Data/Vector.hs
--- a/Data/Vector.hs
+++ b/Data/Vector.hs
@@ -149,7 +149,7 @@
 vcross (Vector3 x1 y1 z1) (Vector3 x2 y2 z2) = Vector3
   {
     v3x = y1 * z2   -   y2 * z1,
-    v3y = x1 * z2   -   x2 * z1,
+    v3y = z1 * x2   -   z2 * x1,
     v3z = x1 * y2   -   x2 * y1
   }